(1) Field of the Invention
The present invention relates to a recording media discharging device for use in a paper discharging portion of an ink-jet printer, for example, as well as relating to an ink-jet printer with the discharging device. In particular, the present invention is directed to preventing damage to recording media in a discharging device using a star roller for ejecting recording media.
(2) Description of the Prior Art
Generally, in an ink-jet type image forming apparatus (referred to hereinbelow as an ink-jet printer), ink drops are ejected sequentially on the upper surface of recording paper being continuously fed to perform image forming. The recording paper with images formed thereon is discharged and stacked one after another onto the paper output tray by a discharging device.
For example, Japanese Patent Application Laid-Open Hei 6 No. 115195 discloses a discharging device which is comprised of a rubber roller in contact with the undersurface of a recording paper and a star roller in contact with the upper surface (image forming face) of the recording paper. The recording paper is held between and conveyed by these two rollers, whereby the recording paper is discharged to the paper output tray. This rubber roller is a drive roller which is turned by a drive force transmitted from a motor. The star roller is an follower roller, which is turned along with the conveyance of the recording paper. This star roller is formed with discrete projections radially arranged on the peripheral surface thereof parallel to its axis. Formed on the peripheral surface between these projections are recessed portions, which are recesses between the projections. Therefore, only the projections come in contact with the upper surface of the recording paper so as to reduce the contact area of the roller with the upper surface of the recording paper, whereby ink smudges on the recording paper will not occur.
However, when such a star roller is used, there occurs the problem as follows. That is, when the leading part of a recording paper xe2x80x98axe2x80x99 (the portion on the downstream side with respect to the paper feed direction) is held and conveyed by the discharging device as shown in FIG. 1A, and when the center portion of recording paper xe2x80x98axe2x80x99 is held and conveyed by the discharging device as shown in FIG. 1B, a high enough conveying force is given to recording paper xe2x80x98axe2x80x99. When, however, the rear end part of recording paper xe2x80x98axe2x80x99 (the portion on the upstream side with respect to the sheet feed direction) is held and conveyed as shown in FIG. 1C, the leading edge of recording paper xe2x80x98axe2x80x99 comes into contact with a paper output tray xe2x80x98bxe2x80x99, so that the frictional force between this recording paper xe2x80x98axe2x80x99 and output tray xe2x80x98bxe2x80x99 acts as a resistance against conveyance, so that a sufficient enough conveying force cannot be given to recording paper xe2x80x98axe2x80x99. When the holding of recording paper xe2x80x98axe2x80x99 between rubber roller xe2x80x98cxe2x80x99 and star roller xe2x80x98dxe2x80x99 is released from this state, as shown in FIG. 1D, the rear edge of recording paper xe2x80x98axe2x80x99 may abide near the contact point between rubber roller xe2x80x98cxe2x80x99 and star roller xe2x80x98dxe2x80x99 due to insufficiency of the conveying force. Once this situation occurs, there is a risk of the rear edge of recording paper xe2x80x98axe2x80x99 (the upstream edge with respect to the feed direction) dropping into the recessed portion xe2x80x98exe2x80x99 on the peripheral side of the star roller, as shown in FIG. 2A. In detail, since paper output tray xe2x80x98bxe2x80x99 is generally located below the exit port of recording paper xe2x80x98axe2x80x99 in order to allow for beneficial sheet discharge operation. Therefore, in the state that the front end part of recording paper xe2x80x98axe2x80x99 is put in contact with paper output tray xe2x80x98bxe2x80x99 as shown in FIG. 1D, the rear part of recording paper xe2x80x98axe2x80x99 springs upwards, which further promotes the fitting of the rear edge into the recessed portion xe2x80x98exe2x80x99.
Star roller xe2x80x98dxe2x80x99 further rotates from this condition where the rear edge of recording paper xe2x80x98axe2x80x99 has dropped into recessed portion xe2x80x98exe2x80x99, the rear edge of recording paper xe2x80x98axe2x80x99 may get nipped between the edge, designated at xe2x80x98fxe2x80x99 of the exit port (one of the printer casing members) and the projection xe2x80x98gxe2x80x99 on the star roller peripheral side as shown in FIG. 2B and recording paper xe2x80x98axe2x80x99 may be damaged. In general, star roller xe2x80x98dxe2x80x99 is composed of a multiple number of roller elements arranged along the direction perpendicular to the feed direction of recording paper xe2x80x98axe2x80x99 (perpendicular to the document surface of FIGS. 2A and 2B), so recording paper xe2x80x98axe2x80x99 is damaged at multiple sites along its rear edge, thus making it impossible to provide a beneficial printout. In this way, the discharging device of the conventional ink-jet printers has not yet provided sufficiently reliable paper discharge performance.
The present invention has been devised in view of what has been discussed above, it is therefore an object of the present invention to provide a discharging device using a star roller, which can realize a beneficial discharge operation by avoiding recording paper being damaged by the rear edge of recording paper dropping into the recessed portions on the peripheral side of the star roller.
In order to achieve the above object, the present invention prevents the rear edge from dropping into recessed portions of the star roller by guiding the rear edge of the recording medium in the discharge direction when the recording medium passes the star roller.
Specifically, the present invention is featured as follows:
In accordance with the first aspect of the present invention, a recording media discharging device using a star roller for conveying recording media with images formed thereon in the discharge direction, includes: guide means for guiding the upstream edge of a recording medium with respect to the feed direction so that the edge will not drop into the recessed portions on the peripheral side of the star roller when the edge passes the star roller.
In accordance with the second aspect of the present invention, the recording media discharging device having the above first feature is characterized in that the star roller is comprised of multiple elements arranged at separate positions on the rotary shaft that is extended perpendicularly to the feed direction of recording media, and as the guide means a pair of guide elements are arranged close to each star roller element and on both sides thereof with respect to the extended direction of the rotary shaft.
In accordance with the third aspect of the present invention, the recording media discharging device having the above first feature is characterized in that the guide means has a guide surface for guiding the upstream edge of a recording medium with respect to the feed direction, and this guide surface is provided with a slant which is inclined gradually up in the paper discharge direction, thereby prevents the edge of the recording medium from dropping into the recessed portions of the star roller while permitting the edge of the recording medium to jump upwards.
In accordance with the fourth aspect of the present invention, the recording media discharging device having the above second feature is characterized in that the guide means has a guide surface for guiding the upstream edge of a recording medium with respect to the feed direction, and this guide surface is provided with a slant which is inclined gradually up in the paper discharge direction, thereby prevents the edge of the recording medium from dropping into the recessed portions of the star roller while permitting the edge of the recording medium to jump upwards.
In accordance with the fifth aspect of the present invention, the recording media discharging device having the above first feature further includes: a conveying roller for holding and conveying recording media between itself and the star roller and is characterized in that the level distance between the outer peripheral surface of the conveying roller and the bottom of the guide means is set to be equal to or shorter than the interval between adjacent projections formed on the peripheral surface of the star roller element.
In accordance with the sixth aspect of the present invention, the recording media discharging device having the above second feature further includes: a conveying roller for holding and conveying recording media between itself and the star roller and is characterized in that the level distance between the outer peripheral surface of the conveying roller and the bottom of the guide means is set to be equal to or shorter than the interval between adjacent projections formed on the peripheral surface of the star roller element.
In accordance with the seventh aspect of the present invention, the recording media discharging device having the above third feature further includes: a conveying roller for holding and conveying recording media between itself and the star roller and is characterized in that the level distance between the outer peripheral surface of the conveying roller and the bottom of the guide means is set to be equal to or shorter than the interval between adjacent projections formed on the peripheral surface of the star roller element.
In accordance with the eighth aspect of the present invention, the recording media discharging device having the above fourth feature further includes: a conveying roller for holding and conveying recording media between itself and the star roller and is characterized in that the level distance between the outer peripheral surface of the conveying roller and the bottom of the guide means is set to be equal to or shorter than the interval between adjacent projections formed on the peripheral surface of the star roller element.
In accordance with the ninth aspect of the present invention, an ink-jet printer includes: a recording media discharging device including: a star roller for conveying recording media with images formed thereon in the discharge direction; and guide means for guiding the upstream edge of a recording medium with respect to the feed direction so that the edge will not drop into the recessed portions on the peripheral side of the star roller when the edge passes the star roller, wherein an image is formed on the upper surface of the recording medium by ejecting ink droplets from an image forming means, and the recording medium with an image formed thereon is discharged toward an output portion by the recording media discharging device.
In accordance with the tenth aspect of the present invention, the ink-jet printer having the above ninth feature is characterized in that the star roller is comprised of multiple elements arranged at separate positions on the rotary shaft that is extended perpendicularly to the feed direction of recording media, and as the guide means a pair of guide elements are arranged close to each star roller element and on both sides thereof with respect to the extended direction of the rotary shaft.
In accordance with the eleventh aspect of the present invention, the ink-jet printer having the above ninth feature is characterized in that the guide means has a guide surface for guiding the upstream edge of a recording medium with respect to the feed direction, and this guide surface is provided with a slant which is inclined gradually up in the paper discharge direction, thereby prevents the edge of the recording medium from dropping into the recessed portions of the star roller while permitting the edge of the recording medium to jump upwards.
In accordance with the twelfth aspect of the present invention, the ink-jet printer having the above tenth feature is characterized in that the guide means has a guide surface for guiding the upstream edge of a recording medium with respect to the feed direction, and this guide surface is provided with a slant which is inclined gradually up in the paper discharge direction, by permitting the edge of the recording medium to jump upwards, thereby prevents the edge of the recording medium from dropping into the recessed portions of the star roller while permitting the edge of the recording medium to jump upwards.
In accordance with the thirteenth aspect of the present invention, the ink-jet printer having the above ninth feature is characterized in that the recording media discharging device further includes: a conveying roller for holding and conveying recording media between itself and the star roller and the level distance between the outer peripheral surface of the conveying roller and the bottom of the guide means is set to be equal to or shorter than the interval between adjacent projections formed on the peripheral surface of the star roller element.
In accordance with the fourteenth aspect of the present invention, the ink-jet printer having the above tenth feature is characterized in that the recording media discharging device further includes: a conveying roller for holding and conveying recording media between itself and the star roller and the level distance between the outer peripheral surface of the conveying roller and the bottom of the guide means is set to be equal to or shorter than the interval between adjacent projections formed on the peripheral surface of the star roller element.
In accordance with the fifteenth aspect of the present invention, the ink-jet printer having the above eleventh feature is characterized in that the recording media discharging device further includes: a conveying roller for holding and conveying recording media between itself and the star roller and the level distance between the outer peripheral surface of the conveying roller and the bottom of the guide means is set to be equal to or shorter than the interval between adjacent projections formed on the peripheral surface of the star roller element.
In accordance with the sixteenth aspect of the present invention, the ink-jet printer having the above twelfth feature is characterized in that the recording media discharging device further includes: a conveying roller for holding and conveying recording media between itself and the star roller and the level distance between the outer peripheral surface of the conveying roller and the bottom of the guide means is set to be equal to or shorter than the interval between adjacent projections formed on the peripheral surface of the star roller element.
According to the present invention, when the recording medium after image formation is discharged by the star roller in the recording media discharging device, the upstream edge of the recording medium with respect to the feed direction comes in contact with the guide means and is guided thereby when the edge passes the star roller. Therefore, it is possible to prevent the edge part of the recording medium from dropping into the recessed portions on the peripheral surface of the star roller. As a result, it is possible to prevent the edge from being damaged by the projections on the peripheral side of the star roller.
According to the present invention, it is possible to positively prevent the upstream edge, with respect to the feed direction, of the recording medium, from dropping into the recessed portions on the peripheral side of the star roller. For example, as shown in FIG. 10A, when guide element 9 is provided only on one side of star roller element 8, there is a possibility that the side edge on the upstream edge of recording paper P with respect to its feed direction might fail to be guided by paper guide 9 in some cases, depending upon the size or the feed position of recording paper P being conveyed (shown in an imaginary line in the figure). In the present invention, since a pair of guide means 9 and 9 are arranged adjacent to and on both sides of each star roller element 8, it is possible for the guide means 9 to guide the part at the side edge of the upstream edge of recording paper P with respect to its feed direction as shown in FIG. 10B, thus never causing any damage to the recording media.
According to the present invention, it is possible to specifically limit the shape of the guide means for preventing the edge of the recording medium from dropping into the recessed portions of the star roller. Particularly, since the guide surface permits the rear edge of the recording medium to jump up, it is possible to make smooth the discharge movement of the recording medium when the output portion (paper output tray in the case of printer) of recording media is located below the position of the exit port of the recording media. In other words, when the output portion of recording media is located below, the recording media are discharged with their leading edge inclined downward in the discharge direction. The configuration of the present invention permits the upstream edge with respect to the feed direction of recording media to jump up, thus assuring the aforementioned discharging posture, and hence realizing a smooth discharge operation.
According to the present invention, it is possible to avoid such a situation that the edges of the recording media are damaged by the projections on the peripheral side of the star roller, so that a reliable ink-jet printer which can provide beneficial printouts can be obtained.